The present invention relates to the biological production of ortho-aminophenols from nitroaromatic compounds using recombinant bacteria.
Ortho-aminophenols are important building blocks for synthesis of polybenzoxazole polymers and biologically active compounds with potential aerospace applications. 2-Amino-3-hydroxyacetophenone (2AHAP) is an ortho-aminophenol of considerable biological and industrial significance. In particular, 2AHAP is an intermediate in oxidative metabolism of tryptophan in mammals and is a key monomer for the synthesis of 3-amino-4,5-diacetylphenoxazone, a dimer similar to the chromophore contained in actinomycin. A glucoside having excellent UV absorbing and scattering properties in the human lens is derived from 2AHAP and is potentially useful in the synthesis of a variety of compounds such as cosmetic humectants, antioxidants, and tyrosinase activity inhibitors. 2AHAP is a precursor for the synthesis of benzoxaprofen, a nonsteroidal antiinflammatory agent and also a possible precursor for the synthesis of acetal glucosides which are the allele chemicals in some plants. 3-Amino-2-hydroxyacetophenone (3AHAP) is a key feedstock for making 2-acetyl-6-[4-(4-phenylbutoxyl)benzoyl]aminophenol, an important pharmaceutical amide.
Because the above aminophenols are difficult to synthesize chemically and are consequently not commercially available, a biocatalytic synthesis of the compounds would be very useful.
In certain bacteria, the metabolism of nitroaromatic compounds occurs via the partial reduction of the nitro group to yield arylhydroxylamine intermediates which are subsequently converted to aminophenols or 1,2-dihydroxyl aromatic compounds. Pseudomonas pseudoalcaligenes JS45 grows on nitrobenzene (NB) as the sole carbon and nitrogen source by a partially reductive catabolic pathway. NB is reduced by NB nitroreductase to hydroxylaminobenzene (HAB), and HAB mutase then catalyzes the rearrangement of HAB to 2-aminophenol which serves as the substrate for meta-ring cleavage. Applicants previously showed that a combination of NB nitroreductase and HAB mutase from strain JS45 can catalyze the production of ortho-aminophenols from nitroaromatic compounds (see U.S. Pat. No. 6,797,497 incorporated herein by reference). In preliminary studies, partially purified NB nitroreductase and HAB mutase A from strain JS45 transformed 2NAP. The use of purified or immobilized enzymes is problematic, however, because the cofactor, NADPH, is consumed in the reaction. Furthermore, the presence of a ring-cleavage dioxygenase in NB-grown cells of JS45 or cell extracts limits its usefulness for the production of aminophenols.
Accordingly, it is an object of the present invention to provide an improved process for the biological production of ortho-aminophenols without the aforementioned problems.
Other objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.